Toward advanced chiral sensors: Enhanced helicity-dependent photocurrent in ultrathin topological-insulator films
Phys. Rev. Applied 24, 014046 – Published 24 July, 2025
DOI: https://doi.org/10.1103/xljy-n67l
Abstract
Chirality, a fundamental property of asymmetric structures, plays a crucial role in pharmaceutical, biological, and chemical systems, offering a powerful tool for selective screening of organic compounds. Although conventional optical chirality detectors are often bulky and cumbersome, due to their inherent chirality, topological insulators (TIs) offer a promising platform for developing compact yet sensitive devices; however, the complex interplay of photoresponses in TIs can limit the ultimate accuracy of their chirality detection. Here, we reveal that in ultrathin TI films, the overlap of the surface-state wave functions leads to their constructive interference and a strongly amplified photocurrent. By attentively analyzing the symmetries and behavior of competing photoresponses in a thin-film TI, we demonstrate that it is possible to effectively eliminate the unwanted contributions and isolate the helicity-dependent photocurrent (HDPC). Moreover, we show that the HDPC can be further enhanced by optimizing the illumination parameters, sensor strain, and/or back gating. Our findings provide a roadmap for design and optimization of miniaturized, high-performance TI chirality detectors, providing the potential to revolutionize chiral analysis in biomedical and material sciences.
